Ah, okay. I looked over the vgmstream sources now and noticed that both the decode_standard_ima function and frame parsing is a bit different from that in h4m_audio_decode v0.3, so it makes sense if there's a discrepancy in the decoding process.
Frame format 0x03 is used in plenty of other H4M videos from various games, but I think you're right about the decoding function in v0.3 just not handling them appropriately.
So by all means, stick to what you've got if you like it better or whatever. If it generates the exact same output, that's totally fine by me. Just curious though, did you compare *all* of the RE0 disc 1 videos?
so, about those Pikmin vids... the audio codec employed for those vids are not unknown. i managed to connect the dots while examining .stx and .h4m files and i somehow found out that said codec is practically the same codec that was used on .stx files used by the game.
how did i manage to find this out, you ask? here, have a test drive: hvq4_hvqm4.bms
do notice how the output .afc file sounds garbled yet you can still hear literally anything at all. assuming you have vgmstream of course.